Lung cancer is the leading cause of cancer death worldwide. Treatment methods other than surgery are not very efficient and lead to resistance. Thus, insights into the etiology of lung cancer and its progression are urgently needed. Colorectal cancer is another leading cause of cancer-related death and the fourth most common cancer worldwide. The survival and prognosis of colorectal cancer patients depends on the stage of the tumor at the time of diagnosis. Early stages of colorectal cancer can be curable. Unfortunately, over 57% have regional or distant spread of the disease at the time of diagnosis. Despite significant investment and advances in the management of cancer, the five-year survival is only 15% for advanced stage colorectal cancer patients.
Recently, many groups have addressed the mechanisms that drive lung cancer by comparing protein, RNA, and microRNA in tumours with healthy tissue. Besides TP53, the most frequently deleted or mutated gene in lung cancer, components of the p53-ARF pathway are also consistently deleted, mutated, or epigenetically modified. As to the colorectal cancer, the challenges are to understand the molecular basis, and to determine factors that initiate the development, and drive the progression. The molecular events involved in colorectal cancer onset and metastatic progression have only been partially clarified. Recent studies have revealed the potential use of molecular and biochemical markers in colorectal cancer to predict outcome and response to chemotherapy, like MLH1, MSH2, β-Catenin, and p53.
Molecular profiles are emerging as predictive and prognostic parameters in non-small-cell lung cancer (NSCLC), including genes involved in DNA damage repair, such as ERCC1, RRM1, and BRCA1. The upregulated expression of the breast cancer predisposition gene, BRCA1 was proposed as prognostic and predictive marker for response to treatment in NSCLC. Concerning colorectal cancer, the studies of the BRCA1 are mainly limited in colorectal cancer risk and BRCA1 mutations. Several studies attempted to correlate BRCA1 mutations and colorectal cancer risk, but without any clear conclusions. Based on the current limited available evidence, BRCA mutation carriers should be regarded as at high risk for colorectal cancer. However the specific role of BRCA1 expression in colorectal cancer is unclear.
BRCA1 is expressed in many proliferating tissues and acts as a tumour suppressor in DNA repair pathways and cell cycle control. BRCA1 protein stability and function depend on its interaction with BARD1 (BRCA1 associated RING domain protein 1). The BRCA1-BARD1 heterodimer has E3 ubiquitin ligase activity, thus controlling the stability of key target proteins through ubiquitination. BARD1 is also involved in p53-dependent apoptosis, which is deficient in most lung cancers. BARD1 stabilizes p53 and promotes its phosphorylation, and expression of BARD1 is required for proper p53 functioning in signalling towards apoptosis. Thus, BARD1 plays a dual role in tumour suppression, as a binding partner of both BRCA1 and p53. Several studies have shown that BARD1 is upregulated during mitosis, transcriptionally by E2F and posttranslationally by phosphorylation, and importantly, that it is essential for mitosis. According to other studies, both BRCA1 and BARD1 were shown to interact with hMSH2, a gene commonly associated with hereditary nonpolyposis colorectal cancer (HNPCC) and mutations of hMSH2 appear to account for approximately 30-40% of HNPCC. Defects in the BRCA1-hMSH2 signalling process lead to increased susceptibility to tumorigenesis.
WO 98/12327 (Board of Regents, the University of Texas System) discloses several genes, identified in screening assays based upon binding to the breast cancer protein, BRCA1. One of these genes is termed BARD1, a RING protein that interacts with BRCA1 and is envisioned for use in various cancer-related diagnostic and therapeutic methods, particularly those connected with breast, ovarian and uterine cancer.
WO 2008/119802 (Université de Genève) discloses that in gynecological cancers, deletion-bearing isoforms of BARD1 are overexpressed and aberrantly localized to the cytoplasm, and their expression correlated with poor prognosis in breast and ovarian cancer. Structural analysis of these isoforms showed that they lacked the regions that interact with BRCA1 or induce apoptosis. These isoforms are specific to gynecological cancers and are termed as isoforms α, β, η, γ, ε, φ, δ and θ.
Due to the severity and incurability of lung and colorectal cancers, there is still a need to develop an effective detecting method which would allow the identification of these cancers and further allow development of effective methods and compositions for treatment or prevention thereof. The main problem is that to date, no efficient methods or strategies have been developed to overcome this problem.